Investigation of the Roles of NCN and HNO Reactions on NOx Formation in Combustion Processes

在燃烧过程中，NCN自由基和HNO在氮氧化物(NOx)的形成中起着重要的中介作用。用于制定和优化污染物减排策略的详细而复杂的反应机理依赖于许多基本气相反应的精确速率常数参数化。虽然已经做了很多工作来开发NOx生成的亚机制，但近年来已经变得明显的是，在模型中没有正确地实施NCN自由基的快速生成途径。在这个项目的第一个资助期，可以第一次对一些最重要的NCN反应进行直接速率常数测量。将继续对选定的双分子NCN反应进行类似的激波管研究，以组装完整的NCN高温机制。利用激光吸收技术，包括最新开发的中红外探测系统，将测量许多物种(NCN、OH、CN、HCN、CH、N)的浓度-时间分布。此外，还将进行额外的实验，以澄清NCN的生成热值和高温吸收截面的一些有争议的值。所有数据的组合导致了一个纯粹基于实验的NCN子机制，该机制将通过更复杂的反应系统的实验进行验证，并应用到现代火焰机制中。火焰模拟将显示是否会达到总体研究目标，即对火焰中NOx形成的可靠模拟。在HNO方面，在第一个资助期内，这种难以测量的物种可能第一次在冲击波后被探测到。进一步优化调频检测系统将能够测量选定的HNO反应的速率常数，包括HNO+O2、H和OH。到目前为止，关于HNO动力学的高温数据很少，而且大部分是分散的；因此，这些测量为改进的HNO火焰模型提供了基础，既可以用于瞬发NO的形成，也可以用于燃料N的转化。

NCN radicals and HNO play important roles as intermediates in the formation of nitrogen oxides (NOx) in combustion processes. The detailed and complex reaction mechanisms used to develop and optimize pollutant reduction strategies rely on accurate rate constant parametrizations for many elementary gas phase reactions. Although much work has been done to develop NOx formation submechanisms, in recent years it has become clear that the NCN radical pathway to prompt-NO formation is not properly implemented in the models.During the first funding period of this project, direct rate constant measurements of some of the most important NCN reactions could be performed for the first time. Similar shock tube investigations of selected bimolecular NCN reactions will be continued in order to assemble a complete NCN high temperature mechanism. Using laser absorption techniques, including a newly developed mid-IR detection system, concentration-time profiles of many species (NCN, OH, CN, HCN, CH, N) will be measured. Moreover, additional experiments will be performed to clarify the somewhat disputed values of the enthalpy of formation and the high temperature absorption cross section of NCN. The combination of all data result in a purely experimentally based NCN submechanism that will be validated against experiments of more complex reaction systems and implemented into modern flame mechanisms. Flame simulations will show if the overarching research goal, i.e. a reliable modeling of NOx formation in flames, will be met. In terms of HNO, during the first funding period this difficult to measure species could be detected behind shock waves for the first time. Further optimization of the frequency modulation detection system will enable rate constant measurements of selected HNO reactions including HNO + O2, H and OH. So far, high temperature data on HNO kinetics are rare and largely scattered; hence these measurements provide the basis for an improved HNO flame model for both prompt-NO formation and fuel-N-conversion.